DataTable转换成Json

using Newtonsoft.Json; //这个google 下。
   public static string DtToSON(DataTable dt)
        {
            StringBuilder jsonSB = new StringBuilder();
            StringWriter sw = new StringWriter(jsonSB);
            JsonWriter jWriter = new JsonWriter(sw);
            jWriter.Formatting = Newtonsoft.Json.Formatting.None;
            jWriter.WriteStartObject();
            int cnt = 0;
            if (dt != null)
            {
                cnt = dt.Rows.Count;
            }


         

            jWriter.WritePropertyName(dt.TableName);
            jWriter.WriteStartArray();
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                jWriter.WriteStartObject();
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    jWriter.WritePropertyName(dt.Columns[j].ColumnName);
                    jWriter.WriteValue(dt.Rows[i][j].ToString());
                }
                jWriter.WriteEndObject();
            }
            jWriter.WriteEndArray();
            jWriter.WriteEndObject();
            return jsonSB.ToString();
        }